The field of gastrointestinal endoscopy has for many years focused on diagnostic and therapeutic techniques to observe, modify and remove tissues located in the digestive tract. General endoscopic procedural techniques such as visualizing, dilating, cutting and manipulating tissue have been accomplished using flexible devices such as endoscopes, balloons, snares and electrosurgical tools well known in the art.
While many of these devices and techniques have been useful in identifying and removing some neoplastic lesions of the mucosal layer as well as providing access to general locations within the digestive tract for the placement of submucosal implants, there are some lesions and areas of the digestive tract which are extremely difficult to resect or access. For example, the en bloc removal of large flat mucosal lesions presents numerous problems for current endoscopic tools and techniques. In addition, to effectively diagnosis some disorders (gastric motility, irritable bowel syndrome, chronic intestinal pseudo-obstruction, etc.) a biopsy of the muscular wall or the myenteric plexus may be necessary. Currently, access to these types of specimens requires full thickness biopsies which can be particularly difficult from an endoscopic approach requiring extremely skilled closure techniques.
There have been some advances in endoscopic techniques to resect flat lesions of the mucosal layer generally termed, Endoscopic Mucosal Resection (EMR). One of these EMR techniques, “lift and cut”, involves the injection of saline or other biocompatible solution beneath the lesion in an attempt to raise the lesion thereby changing the geometry to make it suitable for resection using conventional snare devices.
Modifications to this technique are disclosed in U.S. Pat. No. 5,651,788 in which a lesion is identified and an injection catheter is used to inject saline to elevate the lesion. A ligator is attached to the distal end of the endoscope and suction is applied to the lesion to bring the tissue into the ligator. A ligator band is then applied to the tissue to form a banded mushroom-like polyp which is suitable for removal with an electrosurgical snare.
Alternatively U.S. Pat. No. 5,961,526 discloses a coaxial needle and severing snare assembly in which a needle is used to pierce tissue adjacent a target lesion to elevate the lesion with saline. Once the lesion is elevated, the needle is retracted from the tissue and the snare is extended from the needle lumen to surround the lesion. The lesion is then aspirated into an aspiration cylinder adjacent the distal end of the endoscope and the snare is cinched to sever the tissue surrounding the lesion.
While EMR techniques have been shown to be effective in treating some flat neoplastic lesions there are limitations and complications associated with these techniques. A major limitation associated with this technique is the size of the lesion that can be resected. Generally, these EMR techniques are suitable only for resecting mucosal lesions which are less than 2 cm in diameter. While larger or irregular shaped lesions may be resected in a piecemeal fashion, this is undesirable since small portions of the lesion may remain. Another limitation of these techniques includes uncertainty of the area being resected. Once tissue has been suctioned into a cap ligator or aspiration cylinder, the tissue is directly adjacent the visualization means of the endoscope obscuring the field of view. One complication associated with these EMR techniques is in relation to the use of the needle injection system. Manipulating the injection catheter to position the needle through the mucosal layer into the submucosal layer can ultimately result in puncturing the muscular wall of the digestive tract which may lead to infection or peritonitis. Another complication associated with EMR techniques is damage to the underlying muscular layer. Saline and other non-viscous fluids used to elevate the lesion dissipate relatively quickly after injection into the submucosal layer, such that portions of the underlying muscular layer may be included in the suctioned tissue and inadvertently damaged when using the electrosurgical tool for resection.
In order to overcome some of the size, irregular shapes and visualization limitations associated with EMR techniques, a new procedure called Endoscopic Submucosal Dissection (ESD) has been developed. With this procedure the periphery of the target resection area, which includes the lesion, is marked. An injection catheter is used to deliver a viscous fluid within the submucosal layer, which does not readily dissipate, throughout the target resection area. Once the target resection area has been elevated, an incision is made through the mucosal layer at the edge of the resection area using an electrosurgical needle knife. The physician uses the needle knife to cut the mucosal layer along the periphery of the target resection area. Once the boundary of the resection area has been cut, the physician then uses the needle knife to manually cut the submucosal connective tissue binding the mucosal layer to the muscular wall. Once the physician has completed the submucosal dissection, the mucosal layer is free to be removed in one piece. While this procedure allows the physician to resect large, irregular shaped lesions en bloc, it requires a high degree of skill on the part of the physician and is still subject to the complications associated with needle perforations and muscular layer injury.
In performing the ESD method of resecting a neoplastic lesion, as well as, performing a submucosal medical procedure it is apparent that dissecting the connective tissue of the submucosal space is an important step in having a successful outcome. Numerous investigators have attempted to provide ways of dissecting the submucosal connective tissue.
In U.S. Pat. No. 6,098,629 a method of implanting a submucosal esophageal bulking device is disclosed. The patent further discloses the use of a blunt dissecting member to create a submucosal pocket. In addition, the patent discloses the use of a balloon inserted into the submucosal layer to dissect the submucosal tissue when dilated to form a submucosal pocket.
In PCT Patent Application No. WO 02/089655, methods of implanting submucosal gastric implants are disclosed. The application further discloses various configurations of mechanical and electrosurgical dissection instruments for dissecting the connective tissue of the submucosal layer to form a submucosal pocket in which to place a gastric implant. Included in the description of mechanical dissection instruments are various configurations of balloon dissection instruments.
In U.S. Patent Application No. US2005/0149099, a submucosal dissection instrument, system and method are disclosed. The application further discloses an electrosurgical high frequency knife in combination with a submucosal dissection balloon. Included in the method are the steps of sequentially activating the high frequency knife to create a hole and advancing the balloon assembly into the hole with expansion of the balloon dissecting the connective tissue of the submucosal layer. These steps of the method are repeated until all of the connective tissue beneath the lesion is completely dissected.
With most of the aforementioned disclosed submucosal dissection techniques the physician is required to initially advance a significant portion of a dissection instrument into the submucosal layer while the connective tissue is generally intact. These techniques require that a pushing force be transmitted to the tip of the instrument to dissect the submucosal connective tissue. During application of this pushing force there is a risk that the tip of the instrument may injure or perforate the muscular wall or the mucosal layer.
In performing the disclosed method using the electrosurgical high frequency knife the initial hole through the mucosal layer may be visualized endocopically. Once the balloon assembly is advanced into the submucosal incision hole and expanded to create a cavity, further advancement of the high frequency knife to form a second hole must be conducted without visualization. During the second hole formation and subsequent holes, without visual confirmation of the orientation of the high frequency knife there is a risk of perforating the muscular wall or mucosal layer.